The present invention relates generally to static charge removing systems, and more particularly to a belt toner image or electrostatographic reproduction machines including an effective and economical static charge controlling system.
Static charges, as is well known, ordinarily are generated when two objects are rubbed together. In an electrostatographic reproduction machine that has a belt photoreceptor, it has been found that static charges ordinarily are generated during each revolution when such a belt photoreceptor is driven over objects such as backer bars and rolls. In fact, ordinarily such static charges actually build up revolution after revolution with undesirable machine failure consequences (to be discussed in detail below).
In a typical toner image reproduction machine, for example an electrostatographic printing process machine, portions of a rotatable photoconductive member in the form of a drum or a belt, is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portions of the photoconductive member are exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member thus selectively dissipates the charges thereon in the exposed areas. Such exposure forms an electrostatic latent image on the photoconductive member that corresponds to the informational areas contained within an original document to be reproduced.
After the electrostatic latent image is formed on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a sheet media. The toner particles are then heated to permanently affix the powder image to the sheet media.
The foregoing generally describes a typical black and white electrostatographic printing machine. With the advent of multicolor electrophotography, it is desirable to use a reproduction machine architecture, which comprises a plurality of image forming stations. One example of the plural image forming station architecture utilizes an image-on-image (IOI) system in which the photoreceptive member is recharged, re-imaged and developed for each color separation. This charging, imaging, developing and recharging, re-imaging and developing, all followed by transfer to a sheet, is done in a single revolution of the photoreceptor in so-called single pass machines, while multi-pass architectures form each color separation with a single charge, image and develop, with separate transfer operations for each color.
In either case, particularly where the machine includes a photoconductive or photoreceptive member in the form of a driven web or belt, the web or belt is typically driven over at least a series of rollers. In relatively large such machines, the photoreceptor belt can easily require running over a total of twenty or more backer bars and rubber rolls, during which as pointed out above, it generates static charge during every revolution. The charge generated thus has been found to cause the photoreceptor belt to tend to be attracted to the backer bars and rolls.
Such attraction is exhibited, and can be measured, as an increase in belt drag levels. If such generated static is left uncontrolled, static levels on the back of the belt can become so high, they can cause the belt drag to exceed the drive capacity of the drive rolls and/or of the drive motors. In addition, there are other associated failures that can range from (a) motion quality errors resulting from slip/stick conditions of the belt to the drive rolls, (b) increases in image misregistration, (c) drive motors running out of control and/or stalling due to an excessive motor current fault, and (d) significant charge levels on the photoreceptor belt that can interfere with or hinder a technicians efforts to remove and replace the belt during service.
Therefore there is a need for an effective system for controlling static charge build up on a rotating web or belt, for example, the photoreceptor belt of an electrostatographic reproduction machine.
In accordance with one aspect of the present invention, there is provided a static controlling system is provided for effectively and economically controlling static charge build up on a driven web member moving in contact with support structures. The static controlling system includes (a) at least one resistive contact member for contacting the surface of the driven web member, and (b) a bias source coupled to the resistive contact member for biasing the resistive contact member to apply to the surface of the driven web member a neutralizing bias, having a selected polarity and potential level, thereby effectively neutralizing and controlling static charge build up on the driven web member.
In accordance with another aspect of the present invention there is provided a static controlling system is provided for effectively and economically controlling static charge build up on a driven web member moving in contact with support structures. The static controlling system includes (a) devices for sensing a level and a polarity of static charge build up on a surface of the driven web member, (b) at least one resistive contact member for contacting the surface of the driven web member, and (c) a bias source coupled to the resistive contact member for biasing the resistive contact member to apply to the surface of the driven web member a neutralizing bias, having a selected polarity and potential level, thereby effectively neutralizing and controlling static charge build up on the driven web member.
In accordance with a further aspect of the present invention, there is provided a static controlling system for effectively and economically controlling static charge build up on a driven web member, for example, a driven belt member moving in contact with support structures. The static controlling system includes (a) at least one conductive passive member contacting the driven web member, for example, a driven belt member for dissipating a first degree of static charge from the driven web member, for example, a driven belt member, and (b) an active static removing assembly for additionally dissipating a second and desired degree of static charge from the driven web member, for example, a driven belt member. The active static removing assembly includes a conductive contact member for contacting the driven web member, for example, a driven belt member, and a bias source for biasing the conductive contact member to apply a neutralizing bias, having a selected polarity, to the driven web member, for example, a driven belt member, thereby effectively controlling static charge build up on the driven web member, for example, a driven belt member.
In yet another aspect of the present invention, there is provided an electrostatographic reproduction machine including (a) a series of belt drive and support members, (b) a closed loop belt image bearing member having an imaging surface for carrying a toner image and a backside in contact with the series of belt drive and support members, (c) a sheet supply and handling assembly for moving a copy sheet into a toner image transfer relationship with the closed loop belt image bearing member, (d) imaging devices for forming a toner image on the imaging surface of the closed loop belt image bearing member and transferring the toner image to the copy sheet, and a static controlling system is provided for effectively and economically controlling static charge build up on a driven web member moving in contact with support structures. The static controlling system includes (a) devices for sensing a level and a polarity of static charge build up on a surface of the driven web member, (b) at least one resistive contact member for contacting the surface of the driven web member, and (c) a bias source coupled to the resistive contact member for biasing the resistive contact member to apply to the surface of the driven web member a neutralizing bias, having a selected polarity and potential level, thereby effectively neutralizing and controlling static charge build up on the driven web member.